First, only small gauge (27 G) catheters may be used. Serum or plasma comprises approximately 40-60% of the collected sample volume.īlood sampling via the lateral tail veins may also be performed in the mouse as described here with a few minor modifications. The total blood volume of rodents is 6-7% of their body weight, and no more than 15% of the total blood volume should be collected within a 2 week period. While repeated blood collections may be performed, different sampling sites moving upwards from the base of the tail should be used, and the left and right tail veins should be alternated as sampling sites. The protocol described here may be used for sampling 1 to 4 times per week, but no more than twice per day. Blood collected in less than 3 min from the initiation of restraint provides optimal results. It is recommended that investigators new to this method practice the restraint and tail bleeding techniques in order to minimize the time that experimental animals are restrained. The use of this procedure facilitates compliance with the Animal Welfare Act and the Guide for the Care and Use of Laboratory Animals, which require minimizing the pain and distress that result from laboratory procedures performed on animals. Finally, this procedure minimizes the potential for tissue damage compared to tail tip amputation or retroorbital bleeding. Using the technique described here, up to 1.5 ml of blood may be collected from a rat at a single time point, a volume which readily allows multiple assays to be run in parallel. Second, it offers the ability to collect larger blood volumes than other venipuncture techniques, such as collection from the saphenous or dorsal pedal veins. When blood samples are collected surrounding behavioral procedures, administration of anesthetics is undesirable because it can interfere with learning and memory 4,5. First, it does not require anesthesia, in contrast with sampling from the jugular vein or retroorbital sinus. Here, we describe a quick and simple procedure for obtaining a blood sample from a rat which offers significant advantages over other commonly used techniques. The goal of this method is to obtain blood samples that are minimally influenced by the acute stress response. The aim of this protocol is to describe a blood sampling technique for use in rats that is minimally stressful, does not require anesthesia, allows for multiple blood collections within a single subject, and provides a relatively large sample volume such that multiple assays may be performed on a single sample. Popular techniques for collecting blood such as catheterization of the jugular vein or tail tip amputation do not meet these criteria. The ideal method of blood sampling should have minimal physiological impact on the animal, require no anesthesia, allow rapid and repeated sampling, and provide sufficient blood volume for numerous downstream applications. Rodents are the most commonly used laboratory animal, and multiple methods have been developed for blood collection. Stress hormones and the perception of pain can rapidly alter the composition of the blood. It may also be influenced by the stress induced during the blood sampling procedures itself. Such measures can be influenced by variables that may or may not be critical to the question of interest, including the time of day that the sample is obtained and the gender of the subjects. They may also be used in basic science to assess the “state” of an organism, including the degree of hunger, inflammation, or stress present. By minimizing the stress response and pain resulting from blood sampling, measures can more accurately reflect the true basal state of the animal, with minimal influence from the sampling procedure itself.īiomarkers obtained from blood provide useful diagnostic, predictive, and stratifying measures in many clinical contexts, including cardiovascular disease 1, cancer sciences 2, and psychiatric disease 3. Additionally, it can be used to obtain large volume samples (upwards of 1 ml in some rats), and it may be used repeatedly across experimental days. It permits rapid sampling with minimal pain or invasiveness, without anesthesia or analgesia. This procedure offers significant advantages over other more commonly used techniques. Here we describe a procedure for blood sampling from the lateral tail vein in the rat. One factor that can change the blood composition is the stress response triggered by the sampling procedure, which can contribute to variability in the measures of interest. Blood samples are commonly obtained in many experimental contexts to measure targets of interest, including hormones, immune factors, growth factors, proteins, and glucose, yet the composition of the blood is dynamically regulated and easily perturbed.
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